1. Field of the Invention
The present invention relates to a wrench, and more particularly to a wrench having a safety device.
2. Description of the Related Art
A conventional wrench comprises a shank having an end provided with a drive head, and an adjustable torque mechanism mounted in the shank. The adjustable torque mechanism includes a compression spring mounted in the shank and having an end rested on the locking teeth of the drive head. In operation, the torque of the adjustable torque mechanism is preset, so that when the torque of the drive head exerted on a workpiece exceeds the preset value during operation of the wrench, the locking teeth of the drive head slip, so that the drive head cannot operate the workpiece, thereby providing a safety effect. However, the adjustable torque mechanism is hidden in the shank, so that the user cannot observe operation of the adjustable torque mechanism and easily exerts an excessive force on the wrench, thereby wearing the locking teeth of the drive head.
The closest prior art references of which the applicant is aware are disclosed in Taiwan Patent No. 488354 and U.S. Pat. No. 6,092,442 to Macor.